Zams Rotational Velocities of be Stars

We show that Be stars belong to a high velocity tail of a single B-type star rotational velocity distribution in the main sequence (MS). We studied 127 galactic field Be stars and obtained their true equatorial velocity at the ZAMS using models of stellar evolution with rotation. There is a sharp mass-dependent cut in the ZAMS under which there is no Be star. Velocities above this cut follow a Gaussian-tail distribution. B stars with ZAMS rotational velocities lower than the cut probably cannot become Be.